1. Field
One or more embodiments of the present invention relate to dual mode display-port connectors, and more particularly, to a dual mode display-port connector that connects a host device and a display device according to the display-port communication standards proposed by the Video Electronics Standards Association (VESA).
2. Description of the Related Art
FIG. 1 is a block diagram of a general display-port system according to the display-port communication standards proposed by the Video Electronics Standards Association (VESA). In FIG. 1, reference numerals ‘112’ and ‘122’ denote a display-port interface of a host device 11 and a display-port interface of a display device 12, respectively. The general display-port system will be described with reference to FIG. 1 below.
In a controller 121 included in the display device 12, extended display identification data (EDID) which is configuration data and control information of the display device 12 and display-port configuration data (DPCD) which is reception-condition information of the display device 12 are stored.
A controller 111 included in the host device 11 receives the EDID and the DPCD stored in a serial electrically erasable programmable read-only memory (EEPROM) included in the display device 12 and transmits main data to the controller 121 of the display device 12 based on the EDID and the DPCD, according to the display-port communication standards. Here, the main data means image signals including clock signals.
In the transmission of the main data, the controller 111 of the host device 11 establishes DPCD communication with the controller 121 of the display device 12 according to the display-port communication standards (VESA). The DPCD communication (which is also referred to as communication for link-training) will be summarized below.
First, the controller 111 of the host device 11 transmits planned transmission-condition information of the host device 11 to the controller 121 of the display device 12, based on the DPCD.
Second, the controller 121 of the display device 12 receives the main data based on the transmission-condition information.
Third, when an error occurs during the receiving of the main data, the controller 121 of the display device 12 transmits a signal indicating that transmission conditions are not appropriate for the controller 121 itself to the controller 111 of the host device 11 by using a hot plug detection signal HPD. For example, the controller 121 of the display device 12 transmits the hot plug detection signal HPD of a pulse string including a plurality of logic values ‘1’ and ‘0’ to the controller 111 of the host device 11. While the display device 12 operates normally, the controller 121 of the display device 12 transmits the hot plug detection signal HPD of a logic value ‘1’ to the controller 111 of the host device 11.
Fourth, when the signal indicating that the transmission conditions are not appropriate for the controller 121 is generated using the hot plug detection signal HPD, the controller 111 of the host device 11 changes the planned transmission-condition information of the host device 11 and transmits the changed transmission-condition information to the controller 121 of the display device 12.
Fifth, the second to fourth operations are repeatedly performed.
The display-port interface 112 included in the host device 11 includes a main-data transmission unit 112m and an auxiliary data transceiving unit 112s. 
The main-data transmission unit 112m converts parallel main data received from the controller 111 into differential auxiliary signals, and transmits four pairs of differential auxiliary signals L1+L1−, L2+L2−, L3+L3−, and L4+L4− that consist of eight lines.
The auxiliary data transceiving unit 112s receives a pair of differential auxiliary signals AUX+ and AUX− that consist of two lines from the display device 12, converts the pair of differential auxiliary signals AUX+ and AUX− into parallel input signals according to the display-port communication standards, and inputs the parallel input signals to the controller 111. In contrast, the auxiliary data transceiving unit 112s converts parallel output signals received from the controller 111 into differential auxiliary signals according to the display-port communication standards, and transmits a pair of differential auxiliary signals AUX+ and AUX− that consist of two lines to the display device 12.
In auxiliary data communication as described above, a general single-mode display-port system establishes auxiliary communication using differential auxiliary signals as described above.
However, a dual-mode display-port system establishes auxiliary communication using differential auxiliary signals or inter-integrated circuit (I2C) signals according to a user's selection.
When voltages of a configuration terminal CNF of the host device 11 and a configuration terminal CNF of the display device 12 are low, auxiliary communication is established using the differential auxiliary signals. When the voltages of the configuration terminal CNF of the host device 11 and the configuration terminal CNF of the display device 12 are high, auxiliary communication is established using the I2C signals.
When the configuration terminal CNF of the host device 11 is high and the I2C signals are thus selected, the auxiliary data transceiving unit 112s receives serial data signals SDA from the display device 12, and converts the serial data signals SDA into parallel input signals and inputs the parallel input signal to the controller 111 according to the display-port communication standards. In contrast, the auxiliary data transceiving unit 112s converts parallel output signals received from the controller 111 into serial data signals SDA, and transmits the serial data signals SDA together with a clock signal SCL to the display device 12.
The auxiliary communication using the I2C signals is needed when a display-port interface is switched to a digital visual interface (DVI) or a high-definition multimedia interface (HDMI).
In FIG. 1, reference numeral ‘HPD’ means the hot plug detection signal transmitted from display device 12. Since the hot plug detection signal HPD indicates a logic ‘1’ state while the display device 12 operates, the controller 111 of the host device 11 may thus determine whether the host device 11 is connected to the display device 12 based on the hot plug detection signal HPD.
The controller 121 of the display device 12 transmits the EDID and the DPCD stored according to the display-port communication standards to the controller 111 of the host device 11, and receives the main data from the controller 111 of the host device 11.
The display-port interface 122 included in the display device 12 includes a main data receiving unit 122m and an auxiliary data transceiving unit 122s. 
The main data receiving unit 122m converts four pairs of differential auxiliary signals L1+L1−, L2+L2−, L3+L3−, and L4+L4− that consist of eight lines into parallel input signals and inputs the parallel input signals into the controller 121 according to the display-port communication standards.
In the dual-mode display-port system, when the voltage of the configuration terminal CNF of the display device 12 is low and differential auxiliary signals are thus selected, the auxiliary data transceiving unit 122s converts parallel output signals received from the controller 121 into differential auxiliary signals and transmits a pair of differential auxiliary signals AUX+ and AUX− that consist of two lines to the host device 11, according to the display-port communication standards. In contrast, the auxiliary data transceiving unit 122s receives the pair of differential auxiliary signals AUX+ and AUX− that consist of two lines from the host device 11, and converts these signals into parallel input signals and inputs the parallel input signals to the controller 121 according to the display-port communication standards.
When the voltage of the configuration terminal CNF of the display device 12 is high and the I2C signals are thus selected, the auxiliary data transceiving unit 122s converts parallel output signals received from the controller 121 into serial data signals SDA based on the I2C signals, and transmits the serial data signal SDA to the host device 11. In contrast, the auxiliary data transceiving unit 122s receives the clock signal SCL and the serial data signal SDA from the host device 11, and converts these signals into parallel input signals and inputs the parallel input signals to the controller 121 according to the display-port communication standards.
According to the general dual-mode display-port system described above with reference to FIG. 1, noise or signal attenuation occurs when the EDID and the DPCD are transmitted using the pair of differential auxiliary signals AUX+ and AUX− or the I2C signals to a long distance or when long-distance DPCD communication is established.